6533b831fe1ef96bd129969e

RESEARCH PRODUCT

Simultaneous laser generation and laser ultrasonic detection of the mechanical breakdown of a coating–substrate interface

subject

description

Abstract The present study deals with information that could be obtained by real-time contactless monitoring of the normal displacement, due to the propagation of the longitudinal waves generated by nanosecond pulsed laser irradiation, through a transparent and porous ceramic coating deposited on a metallic substrate. These displacements were recorded in real-time at the rear surface of the specimens using a laser heterodyne interferometer and were correlated with the different steps of laser/material interaction (thermoelastic interactions, fracture of the coating–substrate interface and coating expulsion). An analytical model was developed to establish a relation between the longitudinal waves propagation within the considered system and the recorded normal displacements, and was validated for alumina coatings deposited on stainless steel substrates by atmospheric plasma spraying. Good agreement between calculated and experimental waveforms indicates the potential interest of the proposed technique for the non-destructive characterisation of the ceramic coatings and on estimation of their adhesion strength on metallic substrates.